There are over 170 Flight Masters. For the time being this will be a little horde-centric as I need to take the time to fly around to all of the Alliance Flight masters and get screen shots.

There are different classifications:

Flight Masters

These are the generalized flightpath trainers. The jack of all trades. They haven't specialized like the Wind Rider Masters, the Gryphon Masters, the Bat Handlers or the Dragonhawk Masters.

The breakdown for Flight Masters (Horde Friendly &/or Neutral) has far more Goblins than any other species. Orc is pretty much tied with Human after them and then there's a smattering of others.

Wind Rider Masters

Wind Rider Master seems to be a more specialized branch of flight masters. And Orcs seem to have the closest ties to these creatures since they make up the largest contingent of Wind Rider Masters - almost double of any other Horde race. Taurens are next in number.

Bat Handlers (strictly Undead + 1 Troll)

Dragonhawk Master

Other Flight Masters

Hippogryph and Gryphon Masters- (I still need to fill in Alliance side and add MoP)